The disclosure relates to a control device and to a valve arrangement having the control device.
EP 1 413 810 A1 discloses a control device of the generic type for a turbine valve for controlling the gas or steam supply to a turbine, or a process fitting for controlling a fluid, pitch adjustment for a wind rotor or the like. Control devices such as these normally have a control drive which, in the features of the subject matter of EP 1 413 810 A1, is in the form of an electrical spindle drive. In the case of a gas turbine, an opening cross section of a fitting for adjusting the fuel supply or gas supply, for example, can be adjusted by means of a control device such as this. In an emergency, for example in the event of an electrical power failure or a fault, the fitting—or the pitch angle in the case of a wind rotor—shall be reset, in order to prevent damage to the installation. In the known solution, the spindle drive has an associated toggle lever mechanism for this purpose, which during normal operation, that is to say when the electrical power supply is sufficient, is locked in an extended position, in which a prestressing spring is stressed. This toggle lever acts on a valve body of the fitting (in the case of a gas turbine) or on the control mechanism for setting the pitch angle in the case of a wind rotor. The toggle lever is locked only when the electrical power supply is sufficient; in the event of an electrical power failure, the locking mechanism releases the toggle lever, as a result of which it is moved to its bent position from its extended position via the prestressing spring, and the valve element or the pitch angle adjustment mechanism is reset to its predetermined basic position, corresponding to this adjustment movement.
This solution has the disadvantage that the toggle-lever mechanism requires a considerable amount of physical space and, furthermore, has a relatively complex design, as a result of which the hardware complexity is considerable.
In contrast, the disclosure is based on the object of providing a control device which allows emergency operation with little hardware complexity and with high operational reliability. A control device such as this should also be usable for a valve arrangement, in particular a valve for controlling the steam or gas supply to a turbine or, in general, a process fitting for controlling a process fluid.
This object is achieved by a control device and by a valve arrangement having the features described herein.